The Montane ecosystems: Characteristics and conservation
Esther I. Njiro
University of Nairobi, Institute of African Studies
1997
enjiro@agi.uct.ac.za
Keywords: mountains, conservation, vegetation zones, plant communities,
alpine ecosystems, montane ecosystems.
Introduction
The purpose of this paper is:
To explain to all who love the mountains the different bands of vegetation that
characterise the mountain as one climbs to the top. There may be those who
see the mountains as one mass of plants species mixed in helter skelter
fashion.
To explain the species adaptation to various montane ecosystem zones.
To explain the values of and threats to montane ecosystem and the measures
that could conserve the rich biodiversity.
The information was compiled after a visit to several mountains in Africa.
Mount Kenya, the Abadares, and Mount Marsabit all in Kenya. For the last three
months I have been living on the Table Mountain in Cape Town South Africa. I
have also viewed Mount Kilimanjaro bordering Kenya and Tanzania on close
quarters. The following zones on Fig. 1 were observed:
Nival zone
Alpine zone
Health zone
Hagenia/Hypericum zone
Bamboo zone
Forest
(Savannah) grassland
4300 m
3500 m
3000 m
2800 m
2400 m
Figure 1. The Montane Zones
Characteristics
The soils are distinctly acidic. The humus in the soil is determined by the
moistness of the mountain. The moister the mountain the more the humus.
Where the soil water is close to the surface, there is more vegetation. In Mount
Kenya, for example, soil water is determined by the relief, the depth and the
texture of the soil. On Table Mountain, the water may not be very close to the
surface and there is less vegetation.
Plants are adapted to high radiation levels and low temperatures. During sunny
weather the solar radiation is intense and may cause strong surface heating on
the plants. It is a very fragile ecosystem whereby plants take a long time to
grow because of the low temperatures and poor soils. Some plants have
morphological traits that protect them from strong radiation through
reflection. These include the thick and light coloured indumentum (dense hair)
covering one or both sides of the leaves, and /or bracts, penducles, stems of
plants such as Senecio brassica, Hiechrysum newii among others. These are
more common in the alpine belt than the lower parts of the mountain.
Protection of plants from freezing is achieved through formation of tussocks,
rosettes among other developments. Some grasses e.g. Festuca pilgeri, Agrotis
tryphylla on Mount Kenya have living parts concentrated in the central part
while the outer part consists of dead and decaying leaves and calm bases
offering temperature insulation. During the day, the outermost part of their
leaves are flat and patent while at night they bend inwards towards the centre
of the leaf protecting the centre from low temperatures. Old leaves are not
shed out but remain attached to the stem so as to insulate the plant against
extremes of temperature change.
Another characteristic of the montane ecosystem is thin air. As one rises along
the altitude, the air becomes less dense.
Montane ecosystems have to cope with high radiation, especially in form of
ultra-violet radiation. This is due to clean atmosphere at high level; the
intensity of incoming radiation is greater than in the lowlands. The relative
amount of ultra-violet rays is higher than at sea levels. Cloudiness reduces the
intensity of radiation for at least part of the day. However during a clear
cloudless part of the day, insulation can have adverse affects on lifeforms and
thus the need for specific adaptations.
Montane ecosystems are high rainfall areas. In Eastern Africa, rainfall coincides
with the two maxima of April-May and that of November to December. On the
Table Mountain, there is usually rain in summer and winter. Rainfall is higher
on the lower altitudes of the mountains than on the higher altitudes. Decline in
rainfall on higher altitudes is less marked on Mount Kenya as compared to
Mount Kilimanjaro and the Table Mountain.
Low temperature as altitude increases is another characteristic of montane
ecosystem. The mean temperature decreases by about 0.6°C per 100m
increase in altitude. The most significant variation is the diurnal temperature
in the Afro-Alpine zone. During the day, high temperatures are experienced
due to the direct solar radiation through a clear atmosphere. During the night
there is a strong long wave radiation resulting most often in night frost. This
phenomenon has marked implication on species adaptations in the zone. The
belt experiences rapid temperature change in a day due to changes in wind and
cloudiness (Herdberg 1995).
The montane zones are illustrated by Figure 1 (above). Alpine zone is 3,5004,350m. This is a true mountain region of high rock peaks, tarns and rugged
rocky slopes. Senecio mass flowering occurs only once in every twenty or more
years. Lobelia species are found in groups along wet valley bottoms. The most
conspicuous inhabitant of this zone is Rock Hyrax. Occasionally elephants,
leopards, jackals and buffaloes are found there, particularly in the Eastern
African mountains.
The Nival zone comprises rock and ice. Slopes are usually made of bare gravel
and scree left by glacier erosion. Colourful lichens are the common plant forms
at this altitude. The composite Senecio (Keni opytum) occurs only a few metres
from the glaciers. Helichrysum (browne) occurs on all peaks in cracks of
weathered rocks. The rock hyrax is seen in the lower zone. Figure 2. below
gives a comparative overview between global latitudinal biome and a tropical
montane.
Mountain
Arctic
Temperate
Tundra (heather)
Conifer
Woodland
Deciduous Woodland
Forest
Tropical
Savannah
Figure 2. Global Latitudinal Biome and Tropical Montane ecosystem. (apologies
to the author from the Mountain Forum – the graphic part of this figure did not
reproduce on our web site)
Values of the Mountain Ecosystem
Mountains form some of the most important water catchment areas. Mineral
water, which is considered safe universally, is obtained mainly from mountain
ecosystems. As unique ecosystems, montane ecosystems have fragile and very
rare plant and animal species e.g. the giant Senecio which flowers every 20
years. They provide breeding ground for fish such as trout whose eggs require
very low temperatures (10-14°C) before they hatch. The forests are a source of
construction materials e.g. bamboo, mahogany among others. The montane
ecosystem is a habitat for certain animals which are not found elsewhere.
In lower montane forests (between 2,100-2,400m), the tree species include
camphor (Ocotea usmbarensis), cedar (Juniperus procera), Olive (Olea
africana) and Podocarpus spp. The animals in this region include the giant
forest hog, tree hyrax, white tailed mongoose, elephant, leopard, buffalo,
sykes monkey among others.
Bamboo Zone (2,400-2,800) is the home for giant grass bamboo (Arudinalia
alpina) which grows as thick forest attaining heights of 12-15 metres.
Interspersed are numerous flowering herbs. The Hargenia/Hypericum zone
(2850-3000m) has forests with patches of bamboo thickets and open glades.
Dominant trees include Rosewood (Hagenia abyssinica), Giant St. Johns Wort
(Hypericum keniensis), and Lobelia. The trees are hung with long strands of
lichen, ferns, Sphagnum mosses and orchids. As one goes up the mountain,
there is occurrence of plants that resemble the temperate ferns.
The Heath Zone (3,000-3,500m) is an open moorland of smooth tussock
(Deschampisia flexiosa) and tussock grasses (Eeleusina jaegri) grasses mixed
with other plants varying according to altitude. Giant Herb such as giant
Senecio, Lobelia, giant groundsel and fields for flowers make this zone
particularly attractive.
Apart from the flora and fauna the montane ecosystems have numerous
waterfalls which can be used to generate electricity. They are truly wonderful
areas for recreation as there are several learning resources and delightful
scenery.
Threats to the Montane Ecosystem
The montane ecosystem is threatened by several factors. There is the threat
from human activities such as by mountain climbers. Climbing tracks form
erosion gullies and hikers' feet trample on vegetation which has taken many
years to grow. Mountain climbers are careless with cans, packaging materials,
soap and other forms of human waste. These non-biodegradable waste products
bring chemical pollution and if animals feed on them they cause clogging of
their alimentary canals and they can die. Waste is also unaesthetic.
Commercial overutilisation of trees in the lower forest zones is a great threat
to biodiversity Replanting indigenous trees with fast growing coniferous trees
as has been done on the Table Mountain is not as beautiful as the natural trees.
Wild life is very rare on the Table Mountain as there is not much of natural
vegetation. Lighting the mountain at night for the beautiful scenery for tourists
may bring money to the Cape Town but does not encourage the development of
fauna on Table Mountain.
Global warming is another threat to the montane ecosystems. Snowlines are
receding and eventually there may be a melting of the glaciers which will lead
to drying up of rivers which feed from them.
Human settlement and activities constitute the biggest threat to the mountain
ecosystem. Building of such towns such as Cape Town right inside the mountain
and transporting people by cable car to the peak has eroded the Table
Mountain and driven the flora and fauna as far away as possible. Humans
settlements and land use patterns especially for Eastern African mountains
bring about such threats as fire which when carelessly handled destroys a lot of
biodiversity.
Conservation
Attempts at conservation of montane ecosystem ought to be multifaceted, and
involving several sectors. Since human activities are the greatest threat, there
should be a way of controlling their encroachment. Hikers should be issued
rules of what they can do and cannot do as they visit the montane ecosystems.
Such rules should be enforced with huge fines which will pay for surveillance of
mountain resources.
Gazetting montane ecosystem will be useful in prohibiting excess
overutilisation of forest resources. Religious beliefs and traditions which
protect the environment could be given value by being enforced by the law.
Communities who live by the mountains should benefit from the marketing of
the mountain resources so as to make them enthusiastic custodians of mountain
resources. Cultural centres could be organised by building of museums and
forest homes to cater for tourist and boost the incomes of mountain
communities.
References
Ambio (1996) A Paper on Mount Kenya Forest
Bussman R.W. (1996) Destruction and Management of Mount Kenya Forests in
Ambio Vol 25(5): 6&17 August, p. 314-317.
Hedberg O. (1995) Features of Afro-alpine Plant Ecology, ABC O Ekblad & Co
Vastervik.
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Notes to readers
The author may be reached at:
The Institute of African Studies
University of Nairobi
P.O. Box 30197
Nairobi
Kenya